It certainly looks like people are still taking heed of the old adage that "No one ever got fired for buying IBM": One third of all server spending went to Big Blue in the last quarter, according to IDC's latest Worldwide Quarterly Server Tracker figures, giving it the largest share of the Unix market.

Maybe IBM simply has the most attractive offerings, or maybe the tougher economy means those making purchasing decisions are keener than ever to hang on to their jobs.

If that's the case then it appears there's no equivalent adage about Sun: The company's server revenues declined more than 7 percent year on year. Maybe the rumors about Sun being taken over have had a negative impact on the perception of the company, which may well have affected buying decisions.

The truth is perception plays a large part in most buying decisions, and that goes from choosing a brand of laundry detergent to buy all the way up to deciding what operating systems to run. Just ask Microsoft. The perception is that its Vista OS is a pile of garbage, and Microsoft reckons it's worth spending $100 million on a campaign to try to change that perception.

Why is Vista perceived so badly? In part because Apple has made a concerted effort to create that perception. A campaign featuring Jerry Seinfeld may well succeed in changing this and convincing consumers to run Vista. But will it change the perceptions of IT professionals in large organizations? I wouldn't bet against it. We all like to think we are rational agents, but in reality we are all still susceptible to advertising  even Microsoft's.

Let's take a look at the Linux market. Linux has many things going for it, yet it makes up just 13.4 percent of total server revenue. (Don't forget, many servers run Linux but don't generate revenue for vendors.) There are many sound reasons why Linux may not be appropriate for a given application in a particular organization, but there is little doubt that one of things holding Linux back is that it's taking time for it to be perceived as ready for the big time.

Within the Linux market, the perception of the relative strength of different distributions is as important as objective assessments. The CTO of a very large U.S.-based corporation told me the other day that he chose Red Hat Enterprise Linux for his organization because it was seen as more mature and reliable than SUSE Linux Enterprise Server.

No doubt, RHEL was evaluated and tested thoroughly and compared with SLES, but I suspect his mind was already pretty much made up  he wouldn't get fired for choosing it, if you like.

Last week Red Hat detected an intrusion on certain of its computer systems
and took immediate action ... In connection with the incident, the intruder was able to sign a small number of OpenSSH packages relating only to Red Hat Enterprise Linux 4 (i386 and x86_64 architectures only) and Red Hat Enterprise Linux 5 (x86_64 architecture only).

Of course Red Hat is not the only distribution to have had its servers compromised. A Fedora server was hit at the same time, and Ubuntu and Debian servers  and others  have also been hacked. Nonetheless, an incident like this certainly has the capability to threaten the perception that no one ever got fired for choosing RHEL.

What about Microsoft's server OSes, which still command the largest share of the server market by revenue (36.5 percent), even if growth was a tiny 1.7 percent year on year? There are all sorts of perceptions about these, including insecurity and high cost. For the moment, however, the market share numbers favor Microsoft, so perhaps when it comes to the buying decision, it's a case of safety in numbers  to some degree at least.

Paul Rubens is an IT consultant and journalist based in Marlow on
Thames, England. He has been programming, tinkering and generally
sitting in front of computer screens since his first encounter with a
DEC PDP-11 in 1979.